Composites manufactured by sintering a metal powder and a ceramics powder together are highly tough because of the metal and highly hard and strong because of the ceramics, and are widely used in various applications. For example, WC-Co cemented carbide produced by sintering tungsten carbide (WC) and cobalt (Co) and TiC cermet produced by sintering titanium carbide (TiC) and cobalt (Co) are used as cutting edges of cutters. Niobium carbide (NbC) is occasionally mixed with the above materials.
Ceramic powders for use as materials of composites comprises two-component carbide ceramics comprising a metal element such as WC, TiC, NbC, etc. and C as constituent elements, and two-component nitride ceramics comprising a metal element such as TiN or the like and N as constituent elements. While these ceramics are sufficiently hard themselves, harder ceramics are required in some applications.
Harder materials include diamond, cubic boron nitride (c-BN), etc., for example. In recent years, it has been reported that a thin film of Ti—Al—N three-component ceramics comprising Ti, Al, and N as constituent elements is as hard as c-BN. Specifically, the hardness of Ti—Al—N three-component ceramics is much higher than TiN or AlN, and higher than a sintered body of TiN and AlN.
A thin film of Ti—Al—N three-component ceramics may be manufactured by physical vapor deposition (PVD) or chemical vapor deposition (CVD).
Diamond and c-BN are disadvantageous in that they are not highly oxidization-resistant, are expensive, and hence cause an increase in the cost of manufacture of composites comprising diamond and c-BN. In order to produce a chemically stable, highly hard composite at a low cost, it is effective to use, as the material thereof, a multicomponent ceramics powder comprising two or more metal elements and C or N as constituent elements, such as Ti—Al—N three-component ceramics.
However, Ti—Al—N three-component ceramics has been produced in the form of a thin film by PVD or CVD, and a powder of Ti—Al—N three-component ceramics has not been reported in the art so far.
Attempts to manufacture a multicomponent ceramics powder according to PVD or CVD result in an increase in the cost of manufacture of composites comprising such a multicomponent ceramics powder. The reason for an increase in the cost is that the efficiency with which to produce a multicomponent ceramics powder is low because the PVD and CVD processes have a low reaction efficiency and a low reaction rate. These processes are also problematic in that they need to experimentally determine reactive conditions to produce a powder, and hence are time-consuming and complex.
Another process of producing a Ti—Al—N three-component ceramics powder would be to nitride a mixed powder of Ti and Al. However, the process produces only a mixed powder of TiN and AlN, and fails to manufacture a Ti—Al—N three-component ceramics powder.
Another proposal would be to nitride a Ti—Al two-component alloy. However, the Ti—Al two-component alloy has its surface oxidized by oxygen in the air and hence covered with an oxide film. Since the oxide film makes it extremely difficult to nitride the Ti—Al two-component alloy deeply in its inner structure, the hardness of a composite made of a powder of the produced nitrided Ti—Al two-component alloy is not appreciably increased.
As described above, much difficulty has been experienced in the manufacture of a multicomponent ceramics powder comprising two or more metal elements and C or N as constituent elements, and such a multicomponent ceramics powder has not been available in the art.